1. Field of the Invention
The present invention relates to a method of driving an electric field emission type cold cathode element having at least one electric field emission type cold cathode. Further, the present invention relates to a display apparatus for using the electric field emission type cold cathode element as an electron-generating source.
2. Description of the Related Art
In an electric field emission type cold cathode element, a gate electrode is arranged adjacently to a flat type emitter or a cone-shaped sharp emitter, and a high electric field is concentrated on the emitter through the gate electrode to emit electrons from the emitter.
In this electric field emission type cold cathode element, a current density can be made higher than that of a hot (thermionic) cathode element. The electric field emission type cold cathode element can be applied to a display apparatus needing a high current density, for example, such as a Braun tube and the like. There is a merit that a constant voltage driving and a heater are unnecessary, if the cold cathode element is used as a source of electrons, such as the Braun tube and the like, instead of the hot cathode.
In the display apparatus, the electrons emitted from the emitter are passed in vacuum through an electron lens (including a main lens) mounted above the emitter, and are sent to a (display) screen as an electron beam while deflected by a magnet field provided by a deflection yoke, between the electron lens and the screen. Especially, a color display apparatus usually uses three cold cathodes corresponding to the three primary colors of a red (R), a green (G) and a blue (B). It is required to superimpose three electron beams from the three cold cathodes of R, G and B on the screen to further make a diameter of a beam spot thinner (smaller).
In a usual case, such a color display apparatus employs an in-line structure, namely, a structure in which the three cold cathodes (electron guns) corresponding to the three primary colors are aligned in one lateral row. In such structure, beams emitted from the three electron guns arrive at the screen in the magnetic field. However, the beams are not usually concentrated into one point on the screen under an uniform magnet field. So, in order to concentrate the three electron beams so that they are superimposed on the screen, a magnetic field for the concentration is applied from external portion. That is to say, the beam passed through an outer side is passed through the high-strength magnetic field to be deflected largely. The beam passed through an inner side is passed through the low-strength magnetic field to be deflected small. As a result, the three beams are concentrated into one point on the screen.
A technique of self-convergence has been used for attaining such concentration of the beams on the screen without adjustment. This technique contrives the deflection yoke so that a horizontal deflection magnetic distribution is pincushion-shaped and a vertical deflection magnetic distribution is barrel-shaped to generate a magnetic field combined by the distorted deflection magnetic fields. However, when the electron beams are passed through such magnetic field, the respective beams are distorted by the strongly distorted deflection magnetic field. This distortion causes the generation of aberration referred to as astigmatism or spot coma, which further causes a beam diameter to be larger, and also causes a spot form to be distorted. The following method is proposed with regard to a control to avoid such beam form from being distorted.
That is, for example, Japanese Laid Open Patent Application (JP-A-Heisei, 7-147129) (Patent Publication No.2737616) discloses a technique that divides an emitter array constituting an electric field emission type cold cathode into a plurality of areas, and when a beam spot is located at a center of a display screen which is not distorted, drives only a circular emitter array area, and when the spot is located around a circumference of the display screen, drives the circular emitter array area and a sub emitter array area around it at the same time, and then sets them at a longitudinally long form, and accordingly suppresses the generation of the distortion in the beam spot. However, in this technique, the sizes of the spots of electron beams are different between the center and the circumference of the display screen. This results in a problem that a uniform resolution can not be obtained.
Also, for example, Japanese Laid Open Patent Application (JP-A-Heisei, 9-115426) discloses a technique that mounts a plurality of convergence electrodes around a gate electrode, and corrects a spot form laterally crashed because of distortion of a magnetic field, when electrons are passed through a self-convergence deflection magnetic field. However, this technique generates the magnetic field combined by deflection magnetic fields distorted by making a horizontal deflection magnetic distortion in a pincushion-shaped state and making a vertical deflection magnetic distortion in a barrel-shaped state. Thus, this technique requires a complex deflection yoke. Also, the yoke must be designed for each type of display apparatus. Also, a development method based on an adjustment in an actual sample is used, which leads to the increase of a development period and a development cost. Moreover, the variations between the individual display apparatuses and the mounting ways cause a difference between samples, which easily brings about defective samples having larger beam diameters, and results in a drop of yield.
The present invention is accomplished in view of the above mentioned problems. Therefore, an object of the present invention is to provide a method of driving an electric field emission type cold cathode element that can disuse the horizontal deflection magnetic distribution and the vertical deflection magnetic distribution or can make them smaller, and can suppress the distortion in the beam form caused by the magnetic distribution and the larger (thicker) diameter of the beam spot on the screen, and a display apparatus using this method.
In order to achieve an aspect of the present invention, a method of driving a cold cathode element, includes: (a) providing a plurality of cold cathodes; (b) deflecting a plurality of electron beams respectively emitted from the plurality of cold cathodes; (c) providing at least one control electrode for at least one of the plurality of cold cathodes, wherein an electric field above the control electrode is change d when a voltage is applied to the control electrode; and (d) controlling the voltage applied to the control electrode such that the plurality of electron beams are concentrated on a fluorescent surface.
In this case, the (d) step includes controlling the voltage to be a value close to a voltage applied to one of gate electrodes of the plurality of cold cathodes.
In order to achieve another aspect of the present invention, a method of driving a cold cathode element, includes: (e) providing a plurality of cold cathodes including a first cold cathode and a second cold cathode; (f) deflecting in a deflecting direction a plurality of electron beams respectively emitted from the plurality of cold cathodes; (g) providing at least one control electrode for at least one of the plurality of cold cathodes; and (h) controlling a voltage applied to the control electrode such that a first potential of the first cold cathode is different from a second potential of the second cold cathode, wherein the first potential is a potential difference between a first deflecting side in the deflecting direction and a first opposite side opposite to the first deflecting side above the first cold cathode, and the second potential is a potential difference between a second deflecting side in the deflecting direction and a second opposite side opposite to the second deflecting side above the second cold cathode.
In this case, the (g) step includes providing the control electrode such that an electric field above the control electrode is changed when a voltage is applied to the control electrode.
Also in this case, the (e) step includes providing the plurality of cold cathode such that the first cold cathode is provided nearer in the deflecting direction than the second cold cathode, and wherein the (h) step includes controlling the voltage such that the first potential is lower than the second potential.
Further in this case, the (g) step includes providing a couple of the control electrodes on a deflecting side in the deflecting direction and an opposite side opposite to the deflecting side of each of the plurality of cold cathodes.
In this case, the (g) step includes providing the couple of control electrodes such that the voltage applied to one of the couple of control electrodes is controlled independently of the voltage applied to the other of the couple of control electrodes.
Also in this case, the (g) step includes providing a plurality of the control electrodes around each of the plurality of cold cathodes.
Further in this case, the (g) step includes providing a plurality of the control electrode respectively corresponding to the first deflecting and opposite sides and the second deflecting and opposite sides.
In this case, the (e) step includes providing the plurality of cold cathode such that the first cold cathode is provided nearer in the deflecting direction than the second cold cathode, and wherein the (e) step includes providing the plurality of cold cathodes such that each of the plurality of cold cathodes includes a gate electrode, a plurality of voltages applied to a plurality of the gate electrode corresponding to the plurality of cold cathodes being a same with respect to each other, and wherein the (h) step includes controlling a first deflecting voltage applied to the control electrode corresponding to the first deflecting side to be lower than a first gate voltage applied to the gate electrode of the first cold cathode and controlling a first opposite voltage applied to the control electrode corresponding to the first opposite side to be higher than the first gate voltage and controlling a second deflecting voltage applied to the control electrode corresponding to the second deflecting side to be higher than a second gate voltage applied to the gate electrode of the second cold cathode, and controlling a second opposite voltage applied to the control electrode corresponding to the second opposite side to be lower than the second gate voltage.
In order to achieve still another aspect of the present invention, a method of driving a cold cathode element, includes: (aa) providing three cold cathodes in an in-line arrangement, wherein the three cold cathodes correspond to three primary colors of a red (R), a green (G) and a blue (B), respectively and each of the three cold cathodes includes a gate electrode; (ab) applying a first gate voltage to the gate electrode of the cold cathode, as a R cold cathode, corresponding to the R; (ac) applying a second gate voltage to the gate electrode of the cold cathode, as a G cold cathode, corresponding to the G; (ad) applying a third gate voltage to the gate electrode of the cold cathode, as a B cold cathode, corresponding to the B; (ae) deflecting three electron beams respectively emitted from the three cold cathodes in a deflecting direction along the arrangement proceeding from the B cold cathode to the R cold cathode; (af) providing a first deflecting control electrode in the deflecting direction of the R cold cathode and a first opposite control electrode in a direction opposite to the deflecting direction of the R cold cathode; (ag) providing a second deflecting control electrode in the deflecting direction of the G cold cathode and a second opposite control electrode in the opposite direction of the G cold cathode; (ah) providing a third deflecting control electrode in the deflecting direction of the B cold cathode and a third opposite control electrode in the opposite direction of the B cold cathode; and (ai) controlling a first deflecting voltage applied to the first deflecting control electrode to be lower than the first gate voltage and controlling a first opposite voltage applied to the first opposite control electrode to be higher than the first gate voltage and controlling a second voltage applied to each of the second deflecting and opposite control electrodes equal to the second gate voltage and controlling a third deflecting voltage applied to the third deflecting control electrode to be higher than the third gate voltage, and controlling a third opposite voltage applied to the third opposite control electrode to be lower than the third gate voltage, and wherein when a voltage is applied to each of the first deflecting and opposite control electrodes and the second deflecting and opposite control electrodes, and the third deflecting and opposite control electrodes, an electric field above the each voltage-applied control electrode is changed, respectively.
In order to achieve yet still another aspect of the present invention, a method of driving a cold cathode element, includes: (ba) providing a cold cathode; (bb) deflecting a electron beam emitted from the cold cathode; (bc) providing a control electrode for the cold cathode, wherein an electric field above the control electrode is changed when a voltage is applied to the control electrode; and (bd) controlling the voltage applied to the control electrode such that the electron beam is concentrated on a fluorescent surface.
In this case, the (bd) step includes controlling the voltage such that if a distance between the cold cathode and a position at which the electron beam is radiated on the fluorescent surface is changed to be longer as the result of the (bb) step, the longer the distance, the lower a potential above the cold cathode becomes.
Also in this case, wherein the (bd) step includes controlling the voltage such that if a distance between the cold cathode and a position at which the electron beam is radiated on the fluorescent surface is changed to be longer as the result of the (bb) step, an expansion of the electron beam is suppressed.
Further in this case, wherein the (bd) step includes controlling the voltage such that if a distance between the cold cathode and a position at which the electron beam is radiated on the fluorescent surface is changed to be longer as the result of the (bb) step, a focus point of the electron beam is positioned at a further point.
In this case, the (bd) step includes controlling the voltage to be a lower value when a distance between the cold cathode and a position at which the electron beam is radiated on the fluorescent surface is changed to be longer as the result of the (bb) step.
Also in this case, the (bd) step includes controlling the voltage to be a value close to a voltage applied to a gate electrode of the cold cathode.
Further in this case, the (bc) step includes providing the control electrode which is circular around the cold cathode.
In order to achieve another aspect of the present invention, a method of driving a cold cathode element, includes: (ca) providing a plurality of cold cathodes including a first cold cathode and a second cold cathode; (cb) deflecting in a deflecting direction a plurality of electron beams respectively emitted from the plurality of cold cathodes; (cc) providing first and second control electrodes for at least one of the plurality of cold cathodes; (cd) controlling a first voltage applied to the first control electrode such that a first potential of the first cold cathode is different from a second potential of the second cold cathode, wherein the first potential is a potential difference between a first deflecting side in the deflecting direction and a first opposite side opposite to the first deflecting side above the first cold cathode, and the second potential is a potential difference between a second deflecting side in the deflecting direction and a second opposite side opposite to the second deflecting side above the second cold cathode; and (ce) controlling a second voltage applied to the second control electrode such that if a distance between one of the plurality of cold cathodes and positions at which the plurality of electron beams are radiated on the fluorescent surface is changed to be longer as the result of the (cb) step, the longer the distance, the lower the second voltage becomes.
In order to achieve still another aspect of the present invention, a display apparatus, includes: a plurality of cold cathodes from which a plurality of electron beams are emitted respectively; a fluorescent surface on which the plurality of electron beams are radiated; a control electrode for at least one of the plurality of cold cathodes, wherein an electric field above the control electrode is changed when a voltage is applied to the control electrode; and a control unit controlling the voltage applied to the control electrode such that when the plurality of electron beams are deflected, the plurality of electron beams are concentrated on the fluorescent surface.
In this case, the control unit controls the voltage to be a value close to a voltage applied to one of gate electrodes of the plurality of cold cathodes.
In order to achieve yet still another aspect of the present invention, a display apparatus, includes: a plurality of cold cathodes from which a plurality of electron beams are emitted respectively, wherein the plurality of cold cathodes include a first cold cathode and a second cold cathode; a deflecting unit deflecting in a deflecting direction the plurality of electron beams; a control electrode section for at least one of the plurality of cold cathodes; and a control unit controlling a voltage applied to the control electrode section such that a first potential of the first cold cathode is different from a second potential of the second cold cathode, wherein the first potential is a potential difference between a first deflecting side in the deflecting direction and a first opposite side opposite to the first deflecting side above the first cold cathode, and the second potential is a potential difference between a second deflecting side in the deflecting direction and a second opposite side opposite to the second deflecting side above the second cold cathode.
In this case, an electric field above the control electrode section is changed when a voltage is applied to the control electrode section.
Also in this case, the first cold cathode is provided nearer in the deflecting direction than the second cold cathode, and wherein the control unit controls the voltage such that the first potential is lower than the second potential.
Further in this case, the control electrode section includes a plurality of control electrodes respectively provided on a deflecting side in the deflecting direction and an opposite side opposite to the deflecting side of each of the plurality of cold cathodes.
In this case, a voltage applied to one of a couple of control electrodes corresponding to each of the plurality of cold cathodes of the plurality of control electrodes is controlled by the control unit, independently of a voltage applied to the other of the couple of control electrodes.
Also in this case, a plurality of control electrodes are provided, as the control electrode section, around each of the plurality of cold cathodes.
Further in this case, the plurality of control electrodes are provided respectively corresponding to the first deflecting and opposite sides and the second deflecting and opposite sides.
In this case, the first cold cathode is provided nearer in the deflecting direction than the second cold cathode, and wherein each of the plurality of cold cathodes includes a gate electrode, a plurality of voltages applied to a plurality of the gate electrode corresponding to the plurality of cold cathodes being a same with respect to each other, and wherein the control unit controls a first deflecting voltage applied to the control electrode corresponding to the first deflecting side to be lower than a first gate voltage applied to the gate electrode of the first cold cathode and controls a first opposite voltage applied to the control electrode corresponding to the first opposite side to be higher than the first gate voltage and controls a second deflecting voltage applied to the control electrode corresponding to the second deflecting side to be higher than a second gate voltage applied to the gate electrode of the second cold cathode, and controls a second opposite voltage applied to the control electrode corresponding to the second opposite side to be lower than the second gate voltage.
In order to achieve another aspect of the present invention, a display apparatus, includes: three cold cathodes in an in-line arrangement, wherein the three cold cathodes correspond to three primary colors of a red (R), a green (G) and a blue (B), respectively and each of the three cold cathodes includes a gate electrode; a gate voltage applying unit applying a first gate voltage to the gate electrode of the cold cathode, as a R cold cathode, corresponding to the R, and applying a second gate voltage to the gate electrode of the cold cathode, as a G cold cathode, corresponding to the G;, and applying a third gate voltage to the gate electrode of the cold cathode, as a B cold cathode, corresponding to the B; a deflecting unit deflecting three electron beams respectively emitted from the three cold cathodes in a deflecting direction along the arrangement proceeding from the B cold cathode to the R cold cathode; a first deflecting control electrode in the deflecting direction of the R cold cathode; a first opposite control electrode in a direction opposite to the deflecting direction of the R cold cathode; a second deflecting control electrode in the deflecting direction of the G cold cathode; a second opposite control electrode in the opposite direction of the G cold cathode; a third deflecting control electrode in the deflecting direction of the B cold cathode; a third opposite control electrode in the opposite direction of the B cold cathode; and a control unit controlling a first deflecting voltage applied to the first deflecting control electrode to be lower than the first gate voltage and controlling a first opposite voltage applied to the first opposite control electrode to be higher than the first gate voltage and controlling a second voltage applied to each of the second deflecting and opposite control electrodes equal to the second gate voltage and controlling a third deflecting voltage applied to the third deflecting control electrode to be higher than the third gate voltage, and controlling a third opposite voltage applied to the third opposite control electrode to be lower than the third gate voltage, and wherein when a voltage is applied to each of the first deflecting and opposite control electrodes and the second deflecting and opposite control electrodes, and the third deflecting and opposite control electrodes, an electric field above the each voltage-applied control electrode is changed, respectively.
In order to achieve still another aspect of the present invention, a display apparatus, includes: a cold cathode; a fluorescent surface; a deflecting unit deflecting a electron beam emitted from the cold cathode; a control electrode for the cold cathode, wherein an electric field above the control electrode is changed when a voltage is applied to the control electrode; and a control unit controlling the voltage applied to the control electrode such that the electron beam is concentrated on the fluorescent surface when the electron beam is deflected.
In this case, the control unit controls the voltage such that if a distance between the cold cathode and a position at which the electron beam is radiated on the fluorescent surface is changed to be longer as the result that the electron beam is deflected, the longer the distance, the lower a potential above the cold cathode becomes.
Also in this case, the control unit controls the voltage such that if a distance between the cold cathode and a position at which the electron beam is radiated on the fluorescent surface is changed to be longer as the result that the electron beam is deflected, an expansion of the electron beam is suppressed.
Further in this case, the control unit controls the voltage such that if a distance between the cold cathode and a position at which the electron beam is radiated on the fluorescent surface is changed to be longer as the result that the electron beam is deflected, a focus point of the electron beam is positioned at a further point.
In this case, the control unit controls the voltage to be a lower value when a distance between the cold cathode and a position at which the electron beam is radiated on the fluorescent surface is changed to be longer as the result that the electron beam is deflected.
Also in this case, the control unit controls the voltage to be a value close to a voltage applied to a gate electrode of the cold cathode.
Further in this case, the control electrode is circular provided around the cold cathode.
In order to achieve yet still another aspect of the present invention, a display apparatus, includes: a plurality of cold cathodes including a first cold cathode and a second cold cathode; a deflecting unit deflecting in a deflecting direction a plurality of electron beams respectively emitted from the plurality of cold cathodes; first and second control electrodes provided for at least one of the plurality of cold cathodes; and a control unit controlling a first voltage applied to the first control electrode such that a first potential of the first cold cathode is different from a second potential of the second cold cathode, wherein the first potential is a potential difference between a first deflecting side in the deflecting direction and a first opposite side opposite to the first deflecting side above the first cold cathode, and the second potential is a potential difference between a second deflecting side in the deflecting direction and a second opposite side opposite to the second deflecting side above the second cold cathode, and controlling a second voltage applied to the second control electrode such that if a distance between one of the plurality of cold cathodes and positions at which the plurality of electron beams are radiated on the fluorescent surface is changed to be longer as the result that the plurality of electron beams are deflected, the longer the distance, the lower the second voltage becomes.
In this case, the fluorescent surface is a flat-type.
A first invention of a method of driving an electric field emission type cold cathode element is as follows.
A method of driving an electric field emission type cold cathode element includes: providing an emitter section; mounting a gate electrode (1b) in the vicinity of the emitter section; providing an electric field emission type cold cathode (1) for emitting an electron from the emitter section to the gate electrode (1b) by applying a positive voltage to the emitter section; arraying a plurality of cold cathodes (1) on a line; mounting at least one control electrode (2) in at least one of the plurality of cold cathodes (1); converging an electron beam emitted from the emitter section through an electron lens (4), and then deviating through a magnetic field, and further irradiating to a screen (5); and controlling the control electrode (2), wherein the step of controlling the control electrode (2) controls the control electrode (2) so that a first potential difference at a first cold cathode (1) among the plurality of cold cathodes (1) is different from a second potential difference at a second cold cathode (1) among the plurality of cold cathodes (1), and here the first potential difference implies a potential difference between a reverse deflection side and the deflection side immediately on the first cold cathode (1), and the second cold cathode (1) is located on the reverse deflection side from the first cold cathode (1), and the second potential difference implies a potential difference between the reverse deflection side and the deflection side immediately on the second cold cathode (1).
The step of providing the emitter section provides the emitter section in which a plurality of micro emitters (la) are mounted in a form of array.
The step of controlling the control electrode (2) controls the control electrode (2) so that the second potential difference is lower than the first potential difference.
The step of arraying the plurality of cold cathodes (1) on the line arrays three electric field emission type cold cathodes (1) in order to create the electric field emission type cold cathode element.
The step of mounting the control electrode (2) mounts the control electrodes (2) in forward and backward directions with respect to the array direction of the plurality of cold cathodes (1), for each of the plurality of cold cathodes (1).
A method of driving an electric field emission type cold cathode element includes: providing an emitter section; mounting a gate electrode (1b) in the vicinity of the emitter section; providing an electric field emission type cold cathode (1) for emitting an electron from the emitter section to the gate electrode (1b) by applying a positive voltage to the emitter section; mounting at least one control electrode (2) in the cold cathode (1); converging an electron beam emitted from the emitter section through an electron lens (4), and then deviating through a magnetic field, and further irradiating to a screen (5); and controlling the control electrode (2), wherein the step of controlling the control electrode (2) controls the control electrode (2) so that when the deflection of the electric beam caused by the magnetic field causes a beam irradiation position on the screen (5) to get away, a potential immediately on the cold cathode (1) becomes lower as the beam irradiation position gets away.
The step of controlling the control electrode (2) controls the control electrode (2) in accordance with a deflection angle when the electron beam is deflected by the magnetic field.
Moreover, the present invention provides a display apparatus characterized in that the above-mentioned driving method is used to radiate the electron bean to the screen and carry out a display on the screen. On the screen, a light is emitted by the irradiation of the electron beam.